Field of the Invention
The present invention relates to wireless receiving devices and received data restoring devices, and more particularly to wireless receiving devices and received data restoring devices that are used in wireless communication systems that perform multicarrier transmission by a multiple-input and multiple-output (MIMO) system.
Background Art
Wireless communication systems that perform multicarrier transmission are ideally designed so that local oscillator circuits of both a transmitter and a receiver generate the same carrier frequency. In actual environments, however, the carrier frequency of the local oscillator circuit varies between the transmitter and the receiver. Similarly, a sampling frequency of a digital to analog (DA) converter or an analog to digital (AD) converter also varies between the transmitter and the receiver. That is, a received signal that is processed by the receiver contains such frequency offsets.
In wireless communication using an orthogonal frequency division multiplexing (OFDM) system, orthogonality among subcarriers is affected by a frequency offset of a received signal, which causes inter-carrier interference. Accordingly, a technique of correcting a frequency offset in OFDM receiving devices is conventionally proposed.
For example, International Publication No. 2007/091320 discloses that the amount of phase rotation of each symbol is estimated by a guard interval (GI) method, and an oscillating frequency of an oscillation signal that is output to an RF unit is corrected in an analog manner according to the amount of offset of a carrier frequency obtained by the amount of phase rotation.
Japanese Unexamined Patent Publication No. 2000-224134 discloses digital correction of a phase error of each symbol caused by a carrier frequency error and a guard interval period.
Japanese Unexamined Patent Publication No. 2006-108763 discloses digital correction of a change in phase of each OFDM symbol caused by a shift of a sampling frequency between a transmitter and a receiver.